Parallelogram law of forces:
The law of parallelogram is used to determine the resultant of two forces acting at the point of a rigid body in plane and is inclined to each other at the angle of a.
It state that if the two forces acting simultaneously on a particle, be represented in direction and magnitude by the two adjacent sides of a parallelogram then their resultant can be represented in magnitude and direction by diagonal of parallelogram that passes through their point of intersection."